# Which famous mathematical constant can be celebrated on these dates?

Which famous mathematical constant can be celebrated on these dates?

April 11, 2020

April 12, 2021

April 12, 2022

April 12, 2023

April 11, 2024

April 12, 2025

April 12, 2026

April 12, 2027

April 11, 2028

...

Hint:

Pi day is on March 14 (3/14) because 3 is the first digit of pi and the first two digits after the decimal place are 14.

Keeping this in mind, what constant could end up following this pattern?

• rot13(Abgvpr gung gur qnl fuvsgf bar qnl rneyvre va yrnc lrnef, fhttrfgvat gung gur ahzore bs qnlf fvapr gur ortvaavat bs gur lrne vf uryq pbafgnag. Pna'g vzntvar jul gur ahzore "bar uhaqerq naq bar" vf snzbhf, gubhtu.) – Cloudy7 Apr 11 '20 at 17:51
• My birthday is on the 12th of April! And I love maths. – Culver Kwan Apr 12 '20 at 3:07

## 2 Answers

The constant is

$$e\approx 2.71828$$

Because the dates are

equivalent to the 71st of February

• Shouldn't it be the 72nd, not the 71st? – Rand al'Thor Apr 12 '20 at 5:08
• @Randal'Thor It depends if you truncate the number or round. With $\pi$, it's both, but with $e$ you have to choose one (or celebrate both). – DenverCoder1 Apr 12 '20 at 7:28
• @Rand We would, of course, celebrate in the evening. – Daniel Mathias Apr 12 '20 at 12:57

Could it possibly be:

PI?

Since:

The celebration date falls on Day 102 of each calendar year (note the April date being brought forward by 1 in leap years...) meaning that 101 days have been completed since the start of the year. 101 days works out as 3 days over 14 weeks (14*7 = 98). Since pi is equal to 3.14 to 2 decimal places, the coincidence of 3 days and 14 weeks seems to be a nice fit...

• +1, but not the answer I was looking for – DenverCoder1 Apr 11 '20 at 18:05
• Wouldn't it be Day 102? (Unless you consider January 1 as Day 0, of course.) – trolley813 Apr 11 '20 at 18:05
• @trolley813 True - maths failed me there! A small edit will fix that, thanks... – Stiv Apr 11 '20 at 18:06
• Now the answer is broken though, because 102 is no longer 3+98? – im_so_meta_even_this_acronym Apr 12 '20 at 5:26
• @im_so_meta_even_this_acronym On the contrary - the adjusted answer now talks about the number of completed days, which still pans out... – Stiv Apr 12 '20 at 9:28